The present research examined whether consumer product warnings could cause users to comply with safety instructions. Various warning labels are widely used to convey information about hazards associated with products. The influence of warnings on user behavior such as his or her noticing，reading and following the warnings，however，has been not adequately identified. The objectives of this research are to evaluate the effectiveness of the warnings in realistic experiment conditions concerning experimental procedures and locations of warning labels on products，and to determine the factors affecting the user behavior. The warning experiment was conducted utilizing seventy subjects，where they were asked to test usability of a manual spray containing either synthetic detergent or pesticide without informing them of the true purpose of the experiment，and then they were observed using the product. Both warnings instructed users to wear gloves in using the products. The results indicated that both warnings were fully ineffective in users modifying their behavior in such realistic experimental conditions. This seemed to be attributed to the warning labels placed at reverse faces of the products，and to some users complying even without warnings，as well as to the products which were not perceived to be so hazardous. The subjects perceived the likelihood of injury and the cost of complying to be more important in making the decision about whether to comply with the warning.